Experimental comparison of autodyne and heterodyne laser interferometry using a Nd:YVO4 microchip laser

TL;DR

This paper experimentally compares autodyne and heterodyne laser interferometry using a Nd:YVO4 microchip laser, demonstrating that LOFI (autodyne) offers higher signal-to-noise ratios across various conditions, aligning well with theoretical models.

Contribution

It provides the first experimental comparison of autodyne and heterodyne interferometry with a Nd:YVO4 laser, highlighting LOFI's superior performance over a range of powers and noise levels.

Findings

LOFI interferometry shows higher signal-to-noise ratios than heterodyne.

Experimental results agree with theoretical predictions.

LOFI's advantage persists across different laser powers and noise conditions.

Abstract

Using a Nd:YVO4 microchip laser with a relaxation frequency in the megahertz range, we have experimentally compared a heterodyne interferometer based on a Michelson configuration with an autodyne interferometer based on the laser optical feedback imaging (LOFI) method regarding their signal to noise ratios. In the heterodyne configuration, the beating between the reference beam and the signal beam is realized outside the laser cavity while in the autodyne configuration, the wave beating takes place inside the laser cavity and the relaxation oscillations of the laser intensity then play an important part. For a given laser output power, object under investigation and detection noise level, we have determined the amplification gain of the LOFI interferometer compared to the heterodyne interferometer. LOFI interferometry is demonstrated to show higher performances than heterodyne interferometry for a wide range of laser power and detection level of noise. The experimental results are in good agreement with the theoretical predictions.